Manufacture of artificial silk and the like from viscose solutions



I .Paterated Apn 26, 1927. I

UNITED STATES PATENT OFFICE.

'WILIIIAM PORTER DBEAPER, OF LONDON, ENGLAND.

MANUFACTURE OI ARTIFICIAL SILK AND THE LIKE FROM VISGOSE SOLUTIONS.

No Drawing. Application filed April 18, 1925, Serial No. 24,268, and in Great Britain May 2, 1924.

This invention relates to improvements in the production from viscose solutions of artificial silk yarns or filaments such as staple fibre consisting of fine filaments of a size between five demers and down to two 'deniers or even less, as these are prepared by precipitation in an acid-salt bath. I have discovered that fine filaments of the order set out can be produced from a relatively dilute acid-salt bath, when the acidsalt bath (for example a bath such as is described in the s ecification, ofmy British preferably sodium sulphate, to whicha fur Letters Patent 0. 215,028 containing 20 per cent of sodium sulphate, 7 to 14 perbeneficial in the production of ordinary filaments of say six to seven deniers, but I have now found that far better results can be obtained when manufacturing fine denierrfilaments by working with from four to ten percent of zinc salt, as above mentioned, and in an acid-salt bath which contains not less than eighteen per cent of a sodium salt,

ther small amount of ammonium or other sulphate. such as magnesium sulphate; may

be added as required; or the ammonium or other sulphate, such as magnesium sulphate, may replace an equivalent amount of sodium sulphate as desired. The amount of sodium sulphate or other salts is preferably from '20.to .22 per cent of the weight of the bath solution-but may vary between 18 per cent and an upper limit which may approach 32 per cent but which .will be dependent on the amount of zinc and other salt or salts prescut, the total amount of salt of all kinds present being preferably less-than 32 per cent. The sulphuric acid may amount preferably to between nine and thirteen per cent or thereabouts.

I have found that under the above conditions fine filaments can be produced with great facility because it is possible to spin the filaments at much higher rates than at the normal forty-five meters per. minute, since the use of zinc salt in the proportion set forth produces filaments which are in a a more satisfactory physical'condition than those produced with lower proportions of ,zinc salt. The use of a relatively large quantity of zinc salts produces a great dehydrating efiect which results in the production of threads having a crinkly contour and which in conse uence .have a higher elasticity and stren in the newly formed state. These properties are of considerable. importance in the handling of yarns consisting of such fine filaments, or in the handling of the filaments themselves in the case of staple fibre. The production of fine filaments from baths of the concentrations indicated or thereabouts has the further advantage that crystallization of the salts v on the filaments is prevented or reduced. I

When it is desired to act still further upon these freshly produced filaments directly after they leave the precipitation bath, this treatment may be given in say the funnel guider used in centrifugal spinning. The solution used in such subsequent treatment is generally of a reduced concentration and may contain a zinc salt with or without other salts or acids (for example those used in the original bath in conjunction with the zinc salt) or both salts and acids as desired. Or a zinc salt may be absent except so far as this maybe carried for ward from the precipitation bath by the yarn vitself. Or even water alone may be used at this stage with the object of reducing the concentration of zinc salt in the filaments at this early stage. This solution or liquid may be used cold or otherwise as desired.

By workin under the conditions set out or under similar ones, fine filaments can' be produced with ease in a physical condition which is very suitable for subsequent manipulation and treatment and this effect is produced in a bath of relatively low concentration. This bath gives very satisfactory results when worked at a temperature of say 40 to 45 C. when fine filaments can be produced with ease, but other temperatures can be used with almost equally satisfactory results. although it is found in practice that the above mentioned limits generally give the best results.

What I do claim as my invention and desire to secure by Letters Patent is,:-

1. In the manufacture of fine denier artificial filaments from viscose solutions, the

i extrusion of the solution from the spinning I sulphate.

jet into an acid-salt precipitating hath containing not less than four per cent and not more than ten per cent of a zinc salt and substantially twenty one per cent of sodium 2. In the manufacture of fine denier artificial filaments .from viscose solutions, the extrusion of the solution fromthe spinning jet into an acid-salt precipitating bath which contains not less than four per cent and notmore than ten per cent of a zinc salt and not less than eighteen per cent of other salts, such solution being used at a tempera.-

ture of substantially forty two degrees C.

3. In the manufacture of fine denier artificial filaments from viscose solutions, the extrusion of the solution from the spinning jet into an acid-salt precipitating bath containing not less than four per cent and not more than ten per cent of a zinc salt and not less than eighteen per cent of other salts, the filaments after leaving" the precipitating bath being treated with a solution containing zinc sulphate and soluble salt other than zinc sulphate and of a concentration less than eighteen per cent. v

4. In the manufacture of artificial threads of fine denier from viscose solutions, the ex trusion of the "solution from the spinning jet into an acid-salt precipitating bath containing not less than four per cent and not more than ten per cent of a zinc salt and not less than ei 'hteen per cent of other salts the filaments a ter leaving the precipitating bath being treated with a solution containing zinc sulphate, an acid and soluble salt other than zinc sulphate and of a concentration less than eighteen er cent.

Signed at London, Eng and, this 6th day 'of April, 1925. 5

WILLIAM PORTER DREAPER. 

